The present invention relates to a veneer composer operable to convey veneer pieces of small width cut out of log and dried, cut out inferior portions of the veneer piece by a first clipper into a maximum available width, join the veneer pieces end to end to form a long size composed veneer plate, and again cut the composed veneer plate by a second clipper into a predetermined length to form a full size veneer plate.
Conventionally, a veneer composer as shown in FIG. 1 has been used, in which veneer pieces 1a of small width are carried forwardly by plural sets of infeed conveyors 2 which are arranged in parallel to hold the veneer piece from above and below. The veneer pieces usually have some inferior portions therein, such as irregular shaped front and rear edges and/or cracks or knotholes at a mid portion thereof, which have to be cut out before the veneer pieces are composed. To this end, plural sets of detectors 3 such as limit switches or photo-electric switches are provided between the parallel infeed conveyors 2 for detecting the inferior portions of the veneer pieces 1a.
At the forward end of the infeed conveyors 2 is provided a first clipper 4 for cutting each veneer piece into a maximum available width. The clipper 4 is arranged to be controlled by a signal from the detectors 3 to cut the inferior portions of the veneer piece 1a when the veneer piece 1a stops traveling at a predetermined position after passing through the detectors 3.
Provided at the forward portion of the first clipper 4 and the infeed conveyors 2 is a pitching conveyor 5 which is connected at the forward end portion thereof to a rear end pulley of an outfeed conveyor 6 and which is arranged to be able to swing upwardly from a horizontal position about a central axle of the rear end pulley. When the clipper 4 cuts the front irregular edge of the veneer piece 1a, the pitching conveyor 5 swings upwardly and allows the irregular shaped front edge cut out of the veneer piece to fall downwardly. Immediately thereafter, the pitching conveyor 5 returns to the horizontal position to allow the cut veneer piece 1a to travel thereon. When the clipper 4 cuts the rear irregular edge of the veneer piece 1a, the pitching conveyor 5 does not swing upwardly but stays at the horizontal position. The pitching conveyor 5 is provided so as to carry the veneer piece by holding it from above and below.
Along the course of the outfeed conveyor 6 are provided a spot applicator 7 and a thread nozzle 8. The spot applicator 7 applies adhesive agent such as hot melt resin to front and rear ends of the veneer piece, while the thread nozzle 8 supplies an adhesive thread or ribbon onto the upper surface of the veneer piece. Provided forwardly of the thread nozzle 8 are a pair of upper and lower brake rail members 9 which decelerate the traveling speed of the pieces from the outfeed conveyor 6 and adhere cause abutment and adhering of the successively carried veneer pieces end to end to form a composed veneer plate 1b.
At the forward end of the outfeed conveyor 6 is provided a relay conveyor 10, which accepts the composed veneer plate 1b and carries it forwardly onto a gate conveyor 13. Along the course of travel of the composed veneer plate 1b on the relay conveyor 10 and the gate conveyor 13 are provided a second detector 11 such as limit switch or photo-electric switch and a second clipper 12. In this embodiment, the second detector 11 is provided at the rear portion of the gate conveyor 13, and the second clipper 12 is provided between the brake members 9 and the relay conveyor 10. When the composed veneer plate 1b is carried onto the gate conveyor 13 and travels through a predetermined position where the second detector 11 is provided, the front end of the veneer plate 1b is detected by the second detector 11 and then a cutting signal is sent to the second clipper 12 so as to cut out a full size veneer plate 1c from the composed veneer plate after the front end of the composed veneer plate 1b travels beyond the second detector 11 for a predetermined distance. The full size veneer plate 1c cut out of the composed veneer plate 1b falls down from the gate conveyor 13, when the front end of the plate 1c reaches to a predetermined front portion of the gate conveyor 13, and is stacked at such position.
Referring to a practical example of the first detectors 3 for the veneer pieces 1a, detectors 3 comprise several photo-electric tubes connected in such a manner that when an irregular shaped front edge of the veneer piece 1a travels through all of the detectors and prevents all light from being received by the photo-electric tubes, a front edge cutting signal is sent to the first clipper 4, and that when an irregular shaped rear edge of the veneer piece travels through one of the photo-electric tubes to allow the light to be received by such one photo-electric tube, a rear edge cutting signal is sent to the first clipper 4. Thus, the maximum available width of veneer piece 1a is obtained by removing irregular shapes from both front and rear edges thereof.
On the other hand, as to the second detector 11, only one photo-electric tube is sufficient because it is arranged to detect the straightly cut front end of the composed veneer plate 1b.
The first detectors 3 send signals not only to the first clipper 4 but also simultaneously to a driving means of the pitching conveyor 5. The pitching conveyor 5 is controlled by a signal such that when the veneer piece 1a stops moving so as to be cut by the first clipper 4, the pitching conveyor 5 swings up and temporarily stays there and that when the first clipper 4 descends to cut the irregular edge of the veneer piece and then ascends, the pitching conveyor 5 swings down to the horizontal position.
Namely, the signal from the first detectors 3 is sent to an intermittent drive means 15a, which is equipped on a crank axle 14 for ascending and descending the first clipper 4, and is used to cause one rotation of the crank axle 14. At the same time the signal from the first detectors 3 is sent to an intermittent drive means 15b, which is equipped on a crank axle 16 for swinging the pitching conveyor 5, and is used to cause a half rotation of the crank axle 16.
On the other hand, a signal from the second detector 11 is sent to an intermittent drive means 18, which is equipped on a crank axle 17 for ascending and descending the second clipper 12, and used to cause one rotation of the crank axle 17.
The above mentioned conventional veneer composer has the following problems to be solved.
(1) The control system for the conveyors for conveying the veneer piece 1a was a so called open loop system which comprises an electro-magnet clutch brake 19 and a motor 20, as shown in FIG. 1. PA1 (2) According to the conventional veneer composer, in a situation when a position setting operation for cutting the composed veneer plate into full size overlaps with another position setting operation for cutting the irregular shaped rear edge of the veneer piece, the later position setting operation has controlled the both operations simultaneously. Thereby the veneer piece and the composed veneer plate could not be cut correctly at predetermined cutting positions, and an unexpected large amount of cutting errors has occurred. PA1 (3) As mentioned in (2) above, when the position setting operation for cutting the composed veneer plate into full size overlaps with the position setting operation for cutting the irregular shaped rear edge of the veneer piece, not only the outfeed conveyor 6 but also the pitching conveyor 5 stop moving simultaneously for a full size cutting operation. However, at this time, the infeed conveyor 2 is still moving. Therefore, the interval between the preceding veneer piece on the pitching conveyor 5 and the succeeding veneer piece on the infeed conveyor 2 becomes relatively smaller compared with the normal condition. Accordingly, difficulties have often occurred due to the fact that the pitching conveyor 5 opens before the veneer piece 1a completely travels through the pitching conveyor. That is, the rear portion of a veneer piece 1a having been cut to the available width crushed to the ascending first clipper 4 and is destroyed. PA1 (4) According to the conventional veneer composer, when an inferior portion at midportion of a veneer piece 1a, which should be cut out by the first clipper 4, has a width of less than several 10 mm due to cracks in the veneer piece or the like, the position setting operations for cutting the front edge and rear edge of the inferior portion could not be done separately but were controlled at the same time by the position setting operation that comes later.
In such system, an acceleration time (ta) for restarting the conveyor 2 after a cutting operation to intermittently move a veneer piece 1a, and a deceleration time (td) for stopping the conveyor to set the veneer piece at a predetermined position, were both approximately 10 milliseconds, as shown in FIG. 2, because very abrupt acceleration and deceleration were required to perform high speed operation. Therefore, even if the veneer piece is held from above and below by upper and lower conveyor belts while being carried by the infeed conveyor 2, the imbalance of left and right sides of the veneer piece, because of the irregularly shaped front and rear edges thereof, causes unstable slippage of the veneer piece relative to the conveyor belts due to the difference of the friction resistance therebetween, especially by inertia, at the time of acceleration and deceleration of the conveyor 2. Thus, the veneer piece could not be carried and cut as desired, so that the actual front and rear cutting lines shown by solid lines in FIG. 3 have often been inclined relative to the desired cutting lines shown by dotted lines in FIG. 3. Therefore, the actual available width W2 of the veneer piece cut out of the irregular shaped veneer piece 1a became smaller than the the desired maximum available width W1. When the veneer pieces 1a having such inclined front and rear cutting lines are joined end to end to form a composed veneer plate as shown in FIG. 4, opposite sides of the composed veneer plate have irregular shapes similar to saw-tooth shapes. Therefore, the composed veneer plate of a desired transverse length of W3 could not be obtained and had to be cut to the transverse length of W4 as shown in FIG. 4. This resulted in a low production yield.
Namely, referring to FIG. 1, there can occur a situation that after the front end of the composed veneer plate 1b is detected by the second detector 11, the rear irregular edge of the veneer piece 1a is detected by the first detectors 3 before the composed veneer plate stops at a predetermined full size cutting position. On the contrary, there can occur another situation that after the rear irregular edge of the veneer piece 1a is detected by the first detectors, the front end of the composed veneer plate 1b is detected by the second detector before the veneer piece 1a stops at a predetermined cutting position of the rear irregular edge. In both of the above situations the position setting operations for cutting the composed veneer plate 1b and the veneer piece 1a are overlapped with each other.
In each of the above cases, it has been conventional that both of the position setting operations are controlled by a transfer amount control system of the conveyors 2 and 6, wherein a later position setting data is rewritten on a memory in which an earlier position setting data has been written. Thus, the earlier detected data is erased by the later data, and the rewritten later data controls simultaneously both of the position settings of the veneer piece and the composed veneer plate.
Therefore, it sometimes happens that a maximum 40 mm cutting error of the composed veneer plate occurs, which corresponds to the length from the second detector 11 to the predetermined cutting position thereof, and also that a maximum 40 mm cutting error of the veneer piece occurs, which corresponds to the length from the first detectors to the predetermined cutting position of the veneer piece.
That is, the position setting operations for both the front and rear edges of the inferior portion are controlled by a transfer amount control system of the conveyors 2, 5 and 6, wherein a later detected position setting data is rewritten in a memory in which an earlier detected position setting data has been written. Thus, the earlier detected data is erased by the later data and the rewritten later data controls both of the position settings of the veneer piece. Therefore, if there is a small crack less than several 10 mm in width at the midportion of the veneer piece, the front end of the crack is first detected and the first cutting data is written in the memory. Then the rear end of the crack is detected and this second cutting data is written in the memory by overlapping the first written data so that the first data is erased by the second data. Thus, the second data for cutting the rear edge of the inferior portion controls both of the front and rear cutting operations thereof. This of course would cause an inferior product of the composed veneer plate and the final product.